Binding energy of localized biexcitons in quantum wells

A variational calculation of the ground state energy of a biexciton in a GaAs/AlGaAs quantum well is presented. The well width fluctuations leading to trapping of the biexcitons are modeled by a parabolic potential. The results obtained for different well widths are compared with recent experimental data. Good agreement is obtained both for the biexciton binding energy and for the Haynes factor. We find that the structure of a biexciton is similar to the one of the H_2 molecule.Comment: 9 pages, 4 figure

Electrochemical processes and systems: application for tutors

The features of redox reactions and the principles of their balancing according to the medium composition are considered. The basic representations about electrochemical processes and systems are outlined. The reactions and principles of chemical sources of electric energy and electrolysis systems functioning are analyzed. A general idea is given about the chemical properties of metals, corrosion resistance in environments of various aggressiveness, and the protection principles are given. Multivariate tasks and exercises for students, and PhD student’s classroom and independent work are offered. For teachers, PhD students and students of universities of specialties "Chemical technologies and engineering", "Biotechnologies and bioengineering", "Oil and gas engineering and technologies".Розглянуто особливості окисно-відновних реакцій і принципи їх балансування залежно від складу середовища. Викладено фундаментальні уявлення про електрохімічні процеси і системи. Проаналізовано перебіг реакцій і принципи функціонування хімічних джерел електричної енергії та систем електролізу. Узагальнено уявлення щодо хімічних властивостей металів, корозійної стійкості у середовищах різної агресивності та наведено принципи організації захисту від руйнування. Запропоновано багатоваріантні завдання та вправи для аудиторної та самостійної роботи студентів і аспірантів. Розраховано на викладачів, аспірантів і студентів вищих навчальних закладів спеціальностей "Хімічні технології та інженерія”, "Біотехнології та біоінженерія", "Нафтогазова інженерія та технології"

Using planar laser-induced fluorescence to study the phase transformations of two-component liquid and suspension droplets

Using the planar laser-induced fluorescence (PLIF), we performed experiments to determine evaporation dynamics of homogeneous and heterogeneous droplets of liquids, conditions of their boiling, and explosive breakup. For the 1–2 mm water droplets, the distribution of highly non-homogeneous and non-steady temperature field was detected by highspeed cross-correlation video recording and the Tema Automotive software.We identified highly nonlinear dependences of evaporation rate on heating temperature and time as well as water droplet size. For the two-component liquids and water-based suspensions of graphite, we revealed unsteady temperature fields and established mechanisms and regimes of the explosive breakup of the heterogeneous droplets when heated. The regimes differ in the number and dimensions of the emerging gas–liquid fragments as well as the durations of the main stages. The three regimes of warming-up and evaporation of the heterogeneous droplets have been obtained. The explosive breakup of droplets enables provision for the secondary atomization of the liquid with the emergence of an aerosol cloud. The surface area of the liquid increases several-fold. The temperature variations at the water/solid or water/flammable component interfaces were determined corresponding to each boiling and breakup regime. Using the PLIF, we studied reasons and mechanism of the explosive breakup of water droplets with single large carbonaceous inclusions when heated

Membrane-transferring regions of gp41 as targets for HIV-1 fusion inhibition and viral neutralization

12 páginas, 4 figurasThe fusogenic function of HIV-1 gp41 transmembrane Env subunit relies on two different kinds of structural elements: i) a collapsible ectodomain structure (the hairpin or six-helix bundle) that opens and closes, and ii) two membrane- transferring regions (MTRs), the fusion peptide (FP) and the membrane-proximal external region (MPER), which ensure coupling of hairpin closure to apposition and fusion of cell and viral membranes. The isolation of naturally produced short peptides and neutralizing IgG-s, that interact with FP and MPER, respectively, and block viral infection, suggests that these conserved regions might represent useful targets for clinical intervention. Furthermore, MTR-derived peptides have been shown to be membrane-active. Here, it is discussed the potential use of these molecules and how the analysis of their membrane activity in vitro could contribute to the development of HIV fusion inhibitors and effective immunogensThe authors wish to thank financial support obtained from Spanish MICINN (BIO2008- 00772) (JLN) and University of the Basque Country (GIU 06/42 and DIPE08/12) (NH and JLN).Peer reviewe

High etch rate and smooth morphology using a novel chemistry in reactive ion etching of GaN

no abstrac